Diaminopyrazole compounds and the use thereof in the oxidation dyeing of keratinous fibres

ABSTRACT

The invention relates to novel diaminopyrazole compounds having formula (I): wherein R 1  represents a linear or branched C 4 -C 5  alkyl or n-propyl group, or a linear or branched C 3 -C 5  mono or polyhydroxy alkyl group, and the addition salts thereof with a physiologically acceptable acid. The invention also relates to the compositions containing such a compound for the dyeing of keratinous fibers and the method for using said compositions.

[0001] The present invention relates to novel diaminopyrazole compounds,to a composition for the oxidation dyeing of keratin fibers, and inparticular of human keratin fibers such as the hair, comprising at leastone diaminopyrazole compound as oxidation base, and to the oxidationdyeing processes using it.

[0002] It is known practice to dye keratin fibers, and in particularhuman hair, with dye compositions containing oxidation dye precursors,in particular ortho- or para-phenylenediamines, ortho-aminophenols orpara-aminophenols and heterocyclic compounds such as diaminopyrazolederivatives, which are generally referred to as oxidation bases. Theoxidation dye precursors, or oxidation bases, are colorless or weaklycolored compounds which, when combined with oxidizing products, can giverise to colored compounds and dyes by a process of oxidativecondensation.

[0003] It is also known that the shades obtained with these oxidationbases can be varied by combining them with couplers or colorationmodifiers, the latter being chosen in particular from aromaticmeta-diamines, meta-aminophenols, meta-diphenols and certainheterocyclic compounds.

[0004] The variety of molecules used as oxidation bases and couplersmakes it possible to obtain a wide range of colors.

[0005] The so-called “permanent” coloration obtained by means of theseoxidation dyes must moreover satisfy a certain number of requirements.Thus, it must have no toxicological drawbacks and it must allow shadesof the desired strength to be obtained and have good resistance toexternal agents (light, bad weather, washing, permanent-waving,perspiration and friction).

[0006] The dyes must also allow white hairs to be covered, and, lastly,they must be as unselective as possible, i.e. they must allow thesmallest possible differences in coloration to be produced over theentire length of the same keratin fiber, which may indeed be differentlysensitized (i.e. damaged) between its tip and its root. They must alsoshow good chemical stability in the formulations, and must have a goodtoxicological profile.

[0007] Furthermore, for a certain number of applications, dyes thatproduce chromatic shades on the hair are desired.

[0008] Patent applications DE 42 34 885 and 196 46 609 disclose4,5-diaminopyrazole derivatives, which, when used together with variouscouplers, especially benzoxazines, give chestnut-brown shades with blue,red, violet, aubergine or coppery glints.

[0009] However, these dyes do not satisfy all the above requirements.

[0010] The Applicant has now discovered, entirely surprisingly andunexpectedly, that it is possible to obtain dyes, which are capable ofproducing powerful, particularly chromatic, bright and relativelyunselective colorations, which have excellent properties of resistanceto the various attacking factors to which keratin fibers may besubjected, by using as oxidation base the diaminopyrazoles of theformula (I) below or physiologically acceptable salts thereof.

[0011] One subject of the present invention is thus the noveldiaminopyrazoles having the following structure (I):

[0012] in which R₁ denotes a linear or branched C₄-C₅ n-propyl or alkylgroup or a linear or branched C₃-C₅ mono- or polyhydroxyalkyl group.

[0013] A subject of the invention is also the physiologically acceptableacid salts of the compounds of formula (I), such as the hydrochlorides,hydrobromides, sulfates, tartrates, lactates or acetates.

[0014] R₁ preferably denotes a linear or branched n-propyl; butyl orpentyl group; a linear or branched propyl, butyl or pentyl group whichis substituted by 1 to 4 OH radicals, depending on the possibilities ofsubstitution of the groups mentioned above.

[0015] A subject of the invention is also a composition for theoxidation dyeing of keratin fibers, and in particular of human keratinfibers such as the hair, characterized in that it contains, in a mediumthat is suitable for dyeing, as oxidation base, at least onediaminopyrazole of formula (I) above, or acid salts thereo.

[0016] As mentioned above, the colorations obtained with the oxidationdye composition in accordance with the invention are powerful,particularly bright and chromatic. They in particular produce reddershades that are free of or contain very little blue or yellow.Furthermore, they show excellent properties of resistance with respectto the action of various external agents (light, bad weather, washing,permanent-waving, perspiration and friction).

[0017] A subject of the invention is also a process for the oxidationdyeing of keratin fibers using such a dye composition.

[0018] As examples of diaminopyrazoles of formula (I) according to theinvention, mention may be made of the compounds belonging to thefollowing classes: Structure Name Structure Name Structure Name

2-propyl- 2H- pyrazole- 3,4-diamine

2-butyl-2H- pyrazole- 3,4-diamine

2-isobutyl- 2H- pyrazole- 3,4-diamine

2-sec- butyl-2H- pyrazole- 3,4-diamine

2-pentyl- 2H- pyrazole- 3,4-diamine

2-(3- methyl- butyl)-2H- pyrazole- 3,4-diamine

2-(2- methyl- butyl)-2H- pyrazole- 3,4-diamine

2-(1- methyl- butyl)-2H- pyrazole- 3,4-diamine

2-(1,2- dimethyl- propyl)-2H- pyrazole- 3,4-diamine

2-(1,1- dimethyl- propyl)-2H- pyrazole- 3,4-diamine

2-(2,2- dimethyl- propyl)-2H- pyrazole- 3,4-diamine

3-(4,5- diamino- pyrazol-1- yl)propan- 1-ol

1-(4,5- diamino- pyrazol-1- yl)propan- 2-ol

3-(4,5- diamino- pyrazol-1- yl)propane- 1,2-diol

4-(4,5- diamino- pyrazol-1- yl)butan-1- ol

4-(4,5- diamino- pyrazol-1- yl)butan-2- ol

4-(4,5- diamino- pyrazol-1- yl)butan-2- ol

1-(4,5- diamino- pyrazol-1- yl)butane- 2,3-diol

4-(4,5- diamino- pyrazol-1- yl)butane- 1,2-diol

1-(4,5- diamino- pyrazol-1- yl)butane- 2,3-diol

3-(4,5- diamino- pyrazol-1- yl)butan-1- ol

4-(4,5- diamino- pyrazol-1- yl)pentan- 2-ol

2-(4,5- diamino- pyrazol-1- yl)pentan- 3-ol

2-(4,5- diamino- pyrazol-1- yl)pentan- 1-ol

3-(4,5- diamino- pyrazol-1- yl)butane- 1,2-diol

2-(4,5- diamino- pyrazol-1- yl)butane- 1,4-diol

2-(4,5- diamino- pyrazol-1- yl)butane- 1,3-diol

3-(4,5- diamino- pyrazol-1- yl)butane- 1,2,4-triol

3-(4,5- diamino- pyrazol-1- yl)-2- methyl- propan-1-ol

3-(4,5- diamino- pyrazol-1- yl)-2- methyl- propan-1-ol

4-(4,5- diamino- pyrazol-1- yl)butane- 1,2,3-triol

2-(4,5- diamino- pyrazol-1- ylmethyl)- propane- 1,3-diol

3-(4,5- diamino- pyrazol-1- yl)-3- methyl- butan-2-ol

2-(4,5- diamino- pyrazol-1- yl)-2- methyl- butan-1-ol

3-(4,5- diamino- pyrazol-1- yl)-3- methyl- butane-1,2- diol

2-(4,5- diamino- pyrazol-1- yl)-2- methyl- butane-1,4- diol

2-(4,5- diamino- pyrazol-1- yl)-2- methyl- pentane- 1,3-diol

3-(4,5- diamino- pyrazol-1- yl)-3- methyl- butane- 1,2,4-triol

3-(4,5- diamino- pyrazol-1- yl)-2,2- dimethyl- propan-1-ol

3-(4,5- diamino- pyrazol-1- yl)-3- methyl- butan-1-ol

2-(4,5- diamino- pyrazol-1- ylmethyl)- 2-methyl- propane- 1,3-diol

2-(4,5- diamino- pyrazol-1- yl)-3- methyl- butan-1-ol

2-[1-(4,5- diamino- pyrazol-1- yl)ethyl]- propane- 1,3-diol

5-(4,5- diamino- pyrazol-1- yl)pentan- 1-ol

5-(4,5- diamino- pyrazol-1- yl)pentan- 2-ol

1-(4,5- diamino- pyrazol-1- yl)pentan- 3-ol

1-(4,5- diamino- pyrazol-1- yl)pentan- 2-ol

3-(4,5- diamino- pyrazol-1- yl)-2- methyl- butan-1-ol

5-(4,5- diamino- pyrazol-1- yl)pentane- 1,2-diol

5-(4,5- diamino- pyrazol-1- yl)pentane- 1,3-diol

5-(4,5- diamino- pyrazol-1- yl)pentane- 1,4-diol

1-(4,5- diamino- pyrazol-1- yl)pentane- 2,3-diol

5-(4,5- diamino- pyrazol-1- yl)pentane- 2,3-diol

1-(4,5- diamino- pyrazol-1- yl)pentane- 2,4-diol

5-(4,5- diamino- pyrazol-1- yl)pentane- 1,2,3-triol

4-(4,5- diamino- pyrazol-1- yl)pentan- 1-ol

4-(4,5- diamino- pyrazol-1- yl)pentan- 2-ol

2-(4,5- diamino- pyrazol-1- yl)pentan- 3-ol

2-(4,5- diamino- pyrazol-1- yl)pentan- 1-ol

4-(4,5- diamino- pyrazol-1- yl)pentane- 1,2-diol

4-(4,5- diamino- pyrazol-1- yl)pentane- 1,2,3-triol

4-(4,5- diamino- pyrazol-1- yl)pentane- 1,2,3,5- tetraol

4-(4,5- diamino- pyrazol-1- yl)-3- methyl- butan-1-ol

4-(4,5- diamino- pyrazol-1- yl)-3- methyl- butan-2-ol

2-(4,5- diamino- pyrazol-1- ylmethyl)- butan-1-ol

1-(4,5- diamino- pyrazol-1- yl)-2- methyl- butan-1-ol

4-(4,5- diamino- pyrazol-1- yl)-3- methyl- butane-1,2- diol

3-(4,5- diamino- pyrazol-1- ylmethyl)- butane- 1,2,4-triol

5-(4,5- diamino- pyrazol-1- yl)-pentane- 1,2,3,4- tetraol

4-(4,5- diamino- pyrazol-1- yl)-2- methyl- butan-1-ol

1-(4,5- diamino- pyrazol-1- yl)-3- methyl- butan-2-ol

2-(4,5- diamino- pyrazol-1- yl)-3- methyl- butane-1,4- diol

2-[2-(4,5- diamino- pyrazol-1- yl)ethyl]- propane- 1,3-diol

4-(4,5- diamino- pyrazol-1- yl)-2- methyl- butane-1,3- diol

4-(4,5- diamino- pyrazol-1- yl)-2- hydroxy- methyl- butane-1,3- diol

2-(4,5- diamino- pyrazol-1- yl)-3- hydroxy- methyl- butane-1,4- diol

3-(4,5- diamino- pyrazol-1- yl)-2- methyl- butan-1-ol

2-(4,5- diamino- pyrazol-1- yl)-3- methyl- butan-1-ol

2-[1-(4,5- diamino- pyrazol-1- yl)ethyl]- propane- 1,3-diol

2-(4,5- diamino- pyrazol-1- yl)-3- methyl- butane-1,4- diol

[0019] The diaminopyrazoles of formula (I) that are preferred accordingto the invention have the following structures: Structure Name StructureName Structure Name

2-propyl- 2H- pyrazole- 3,4-diamine

2-butyl-2H- pyrazole- 3,4-diamine

2-isobutyl- 2H- pyrazole- 3,4-diamine

2-sec- butyl-2H- pyrazole- 3,4-diamine

2-pentyl- 2H- pyrazole- 3,4-diamine

2-(3- methyl- butyl)-2H- pyrazole- 3,4-diamine

2-(2- methyl- butyl)-2H- pyrazole- 3,4-diamine

2-(1- methyl- butyl)-2H- pyrazole- 3,4-diamine

2-(1,2- dimethyl- propyl)-2H- pyrazole- 3,4-diamine

2-(1,1- dimethyl- propyl)-2H- pyrazole- 3,4-diamine

2-(2,2- dimethyl- propyl)-2H- pyrazole- 3,4-diamine

3-(4,5- diamino- pyrazol-1- yl)propan- 1-ol

1-(4,5- diamino- pyrazol-1- yl)propan- 2-ol

3-(4,5- diamino- pyrazol-1- yl)propane- 1,2-diol

4-(4,5- diamino- pyrazol-1- yl)butan-1- ol

4-(4,5- diamino- pyrazol-1- yl)butan-2- ol

4-(4,5- diamino- pyrazol-1- yl)butane- 1,2-diol

1-(4,5- diamino- pyrazol-1- yl)butane- 2,3-diol

1-(4,5- diamino- pyrazol-1- yl)butane- 2,3-diol

3-(4,5- diamino- pyrazol-1- yl)butan-1- ol

2-(4,5- diamino- pyrazol-1- ylmethyl)- propane- 1,3-diol

2-(4,5- diamino- pyrazol-1- yl)-3- methyl- butan-1-ol

2-[1-(4,5- diamino- pyrazol-1- yl)ethyl]- propane- 1,3-diol

5-(4,5- diamino- pyrazol-1- yl)pentan- 1-ol

5-(4,5- diamino- pyrazol-1- yl)pentane- 1,2-diol

5-(4,5- diamino- pyrazol-1- yl)pentane- 1,3-diol

5-(4,5- diamino- pyrazol-1- yl)pentane- 1,4-diol

5-(4,5- diamino- pyrazol-1- yl)pentane- 2,3-diol

1-(4,5- diamino- pyrazol-1- yl)pentane- 2,4-diol

1-(4,5- diamino- pyrazol-1- yl)pentane- 2,3-diol

4-(4,5- diamino- pyrazol-1- yl)pentan- 1-ol

4-(4,5- diamino- pyrazol-1- yl)-3- methyl- butane-1,2- diol

2-[2-(4,5- diamino- pyrazol-1- yl)ethyl]- propane- 1,3-diol

3-(4,5- diamino- pyrazol-1- yl)-2- methyl- butan-1-ol

3-(4,5- diamino- pyrazol-1- yl)propan- 1-ol

[0020] The diaminopyrazoles of formula (I) that are more particularlypreferred according to the invention are

[0021] 2-propyl-2H-pyrazole-3,4-diamine

[0022] 2-isobutyl-2H-pyrazole-3,4-diamine

[0023] 2-(2,2-dimethylpropyl)-2H-pyrazole-3,4-diamine

[0024] 3-(4,5-diaminopyrazol-1-yl)propan-1-ol

[0025] 1-(4,5-diaminopyrazol-1-yl)propan-2-ol

[0026] 3-(4,5-diaminopyrazol-1-yl)propane-1,2-diol

[0027] 4-(4,5-diaminopyrazol-1-yl)butan-1-ol

[0028] 4-(4,5-diaminopyrazol-1-yl)butane-1,2-diol

[0029] 5-(4,5-diaminopyrazol-1-yl)pentan-1-ol

[0030] or the addition physiologically acceptable acid salts thereof.

[0031] The diaminopyrazoles of formula (I) according to the inventionare prepared, for example, according to the following generalpreparation method:

[0032] The synthetic approach shown below is described in the literatureup to intermediate (2) (J. H. P. Juffermanns, C. L.; Habraken; J. Org.Chem., 1986, 51, 4656; Klebe et al., Synthesis, 1973, 294; R. Huttel, F.Buchele; Chem. Ber., 1955, 88, 1586). The alkylation and the aminationto obtain the compounds of the type (5) of formula (I) according to theinvention are mentioned, for example, in document DE 42 34 885.

[0033] The dye composition according to the invention especiallycontains from 0.001% to 10% by weight, preferably from 0.05% to 6% byweight and even more preferably from 0.1% to 3% by weight of at leastone diaminopyrazole of formula (I) or of the salts thereof.

[0034] The dye composition in accordance with the invention may alsocontain, in addition to the diaminopyrazole(s) defined above, at leastone additional oxidation base that may be chosen from the oxidationbases conventionally used in oxidation dyeing and among which mentionmay be made especially of para-phenylenediamines,bis(phenyl)alkylenediamines, para-aminophenols, ortho-aminophenols andheterocyclic bases other than the 4,5-diaminopyrazoles used inaccordance with the invention.

[0035] Among the para-phenylenediamines that may be mentioned moreparticularly, for example, are para-phenylenediamine,para-tolylenediamine, 2,6-dimethyl-para-phenylenediamine,2-β-hydroxyethyl-para-phenylene-diamine,2-n-propyl-para-phenylenediamine, 2-isopropyl-para-phenylenediamine,N-(β-hydroxypropyl)-para-phenylenediamine,N,N-bis(β-hydroxyethyl)-para-phenylenediamine,4-amino-N-(β-methoxyethyl)aniline and the para-phenylenediaminesdescribed in French patent application FR 2 630 438, and the additionsalts thereof.

[0036] Among the bis(phenyl)alkylenediamines that may be mentioned moreparticularly, for example, areN,N′-bis-(β-hydroxyethyl)-N,N′-bis(4′-aminophenyl)-1,3-diamino-propanol,N,N′-bis(β-hydroxyethyl)-N,N′-bis(4′-amino-phenyl)ethylenediamine,N,N′-bis(4-aminophenyl)tetra-methylenediamine,N,N′-bis(β-hydroxyethyl)-N,N′-bis(4-aminophenyl)tetramethylenediamine,N,N′-bis(4-methyl-aminophenyl)tetramethylenediamine andN,N′-bis(ethyl)-N,N′-bis(4′-amino-3′-methylphenyl)ethylenediamine, andthe addition salts thereof.

[0037] Among the para-aminophenols that may be mentioned moreparticularly, for example, are para-aminophenol, 4-amino-3-methylphenol,4-amino-3-fluorophenol, 4-amino-3-hydroxymethylphenol,4-amino-2-methylphenol, 4-amino-2-hydroxymethylphenol,4-amino-2-methoxy-methylphenol, 4-amino-2-aminomethylphenol and4-amino-2-(β-hydroxyethylaminomethyl)phenol, and the addition saltsthereof.

[0038] Among the ortho-aminophenols that may be mentioned moreparticularly, for example, are 2-aminophenol, 2-amino-5-methylphenol,2-amino-6-methylphenol and 5-acetamido-2-aminophenol, and the additionsalts thereof.

[0039] Among the heterocyclic bases that may be mentioned moreparticularly, for example, are pyridine derivatives, pyrimidinederivatives, pyrazole derivatives other than the diaminopyrazoles offormula (I) used in accordance with the invention, and the additionsalts thereof. When they are used, these additional oxidation basespreferably represent from 0.0005% to 12% by weight relative to the totalweight of the dye composition and even more preferably from 0.005% to 6%by weight relative this weight.

[0040] The oxidation dye compositions in accordance with the inventionmay also contain at least one coupler and/or at least one direct dye,especially to modify the shades or to enrich them with glints.

[0041] The couplers that may be used in the oxidation dye compositionsin accordance with the invention may be chosen from the couplersconventionally used in oxidation dyeing, and among which mention may bemade especially of meta-phenylenediamines, meta-aminophenols,meta-diphenols, mono- or polyhydroxylated naphthalene derivatives andheterocyclic couplers such as, for example, indole or pyridinederivatives, and the addition salts thereof.

[0042] These couplers are chosen more particularly from2-methyl-5-aminophenol, 5-N-(β-hydroxyethyl)amino-2-methylphenol,6-chloro-2-methyl-5-aminophenol, 3-amino-phenol, 1,3-dihydroxybenzene,1,3-dihydroxy-2-methyl-benzene, 4-chloro-1,3-dihydroxybenzene,2,4-diamino-1-(β-hydroxyethyloxy)benzene,2-amino-4-(β-hydroxyethyl-amino)-1-methoxybenzene, 1,3-diaminobenzene,1,3-bis-(2,4-diaminophenoxy)propane, 3-ureidoaniline,3-ureido-1-dimethylaminobenzene, sesamol,1-β-hydroxyethylamino-3,4-methylenedioxybenzene, α-naphthol,2-methyl-1-naphthol, 6-hydroxyindole, 4-hydroxyindole,4-hydroxy-N-methylindole, 2-amino-3-hydroxypyridine,6-hydroxy-benzomorpholine, 3,5-diamino-2,6-dimethoxypyridine,1-N-(β-hydroxyethyl)amino-3,4-methylenedioxybenzene and2,6-bis(β-hydroxyethylamino)toluene, and the addition salts thereof.

[0043] When they are present, these couplers especially represent from0.0001% to 10% of the total weight of the dye composition, preferablyfrom 0.005% to 5% by weight and even more preferably from 0.1% to 3% ofthis weight.

[0044] In general, the addition salts with an acid that may be used inthe context of the dye compositions of the invention (oxidation basesand couplers) are chosen especially from the hydrochlorides,hydrobromides, sulfates, tartrates, lactates and acetates. The additionsalts with a base are especially those obtained with sodium hydroxide,potassium hydroxide, ammonia, amines or alkanolamines.

[0045] The medium that is suitable for dyeing (or support) usedaccording to the invention consists of water or of a mixture of waterand at least one organic solvent chosen from C₁-C₄ lower alkanols,polyols and polyol ethers, aromatic alcohols, similar products andmixtures thereof.

[0046] The dye composition according to the invention may also containvarious adjuvants conventionally used in compositions for dyeing thehair, such as anionic, cationic, nonionic, amphoteric or zwitterionicsurfactants or mixtures thereof, anionic, cationic, nonionic, amphotericor zwitterionic polymers or mixtures thereof, mineral or organicthickeners, antioxidants, reducing agents, sunscreens, penetratingagents, sequestering agents, fragrances, buffers, dispersants,conditioners, for instance silicones, film-forming agents, preservingagents and opacifiers.

[0047] The pH of the dye composition according to the invention isbetween 3 and 12.

[0048] Needless to say, a person skilled in the art will take care toselect this or these optional additional compound(s) such that theadvantageous properties intrinsically associated with the oxidation dyecomposition in accordance with the invention are not, or are notsubstantially, adversely affected by the envisaged addition(s).

[0049] The dye composition according to the invention may be in variousforms, such as in the form of liquids, creams or gels, or in any otherform that is suitable for dyeing keratin fibers, and especially humanhair.

[0050] Another subject of the invention is a process for dyeing keratinfibers, and in particular human keratin fibers such as the hair, usingthe dye composition as defined above.

[0051] According to this process, at least one dye composition asdefined above is applied to the fibers, for a time that is sufficient todevelop the desired coloration, either in air or using an oxidizingagent. The dye composition may optionally contain oxidation catalysts,so as to accelerate the oxidation process.

[0052] According to a first embodiment of the process of the invention,the coloration of the fibers may be performed without adding anoxidizing agent, solely by contact with atmospheric oxygen.

[0053] According to a second embodiment of the process of the invention,at least one dye composition as defined above is applied to the fibers,the color being revealed at acidic, neutral or alkaline pH using anoxidizing agent that is added to the composition just at the time ofuse, or which is present in an oxidizing composition appliedsimultaneously or sequentially in a separate manner.

[0054] According to this second embodiment of the dyeing process of theinvention, the dye composition described above is preferably mixed, atthe time of use, with an oxidizing composition containing, in a mediumthat is suitable for dyeing, at least one oxidizing agent present in anamount that is sufficient to develop a coloration. The mixture obtainedis than applied to the keratin fibers and is left for an action time of3 to 50 minutes and preferably 5 to 30 minutes, after which the fibersare rinsed, washed with shampoo, rinsed again and dried.

[0055] The oxidizing agent present in the oxidizing composition asdefined above may be chosen from the oxidizing agents conventionallyused for the oxidation dyeing of keratin fibers, and among which mentionmay be made of hydrogen peroxide, urea peroxide, alkali metal bromatesand persalts such as perborates and persulfates. Hydrogen peroxide isparticularly preferred.

[0056] The pH of the oxidizing composition containing the oxidizingagent as defined above is such that, after mixing with the dyecomposition, the pH of the resulting composition applied to the keratinfibers preferably ranges between 3 and 12, and even more preferablybetween 5 and 11. It is adjusted to the desired value by means ofacidifying or basifying agents usually used in the dyeing of keratinfibers, and as defined above.

[0057] The oxidizing composition as defined above may also containvarious adjuvants conventionally used in compositions for dyeing thehair and as defined above.

[0058] The composition that is finally applied to the keratin fibers maybe in various forms, such as in the form of liquids, creams or gels, orin any other form that is suitable for dyeing keratin fibers, andespecially human hair.

[0059] Another subject of the invention is a multi-compartment device ordyeing “kit” or any other multi-compartment packaging system, a firstcompartment of which contains the dye composition as defined above, anda second compartment of which contains the oxidizing composition asdefined above. These devices may be equipped with a means for applyingthe desired mixture to the hair, such as the devices described in patentFR-2 586 913 in the name of the Applicant.

[0060] The examples that follow are intended to illustrate the inventionwithout, however, limiting its scope.

EXAMPLES Examples of Synthesis of Compounds of Formula (I)

[0061] Synthesis of 3,4,5-tribromopyrazole (1):

[0062] An aqueous solution (350 ml) containing sodium hydroxide (24 g,0.6 mol) and pyrazole (10 g, 0.147 mol) was prepared with stirring.After cooling the reaction medium to 20° C., Br₂ (72 g, 0.45 mol) wasadded dropwise over 1 hour, while maintaining the temperature between20° C. and 25° C. The reaction was monitored by thin layerchromatography (TLC) (50% hexane/50% EtOAc or ethyl acetate). Theprecipitate was filtered off and washed with demineralized water (100ml). The filtrate was acidified to pH 6-7 using HCl (10%, 33 g, 0.27mol) and maintaining the temperature between 20 and 25° C. Theprecipitate thus formed was filtered off and washed with demineralizedwater (100 ml). The combined solids were maintained at reflux inDean-Stark apparatus in the presence of toluene (200 ml). At the end ofcollection of the water, the organic phase was filtered while hot. Thesolvent was evaporated down to a residual volume of 110 ml. The solutionwas cooled to 0-5° C. for 1 hour. The precipitate formed was collectedby filtration, washed with cold toluene (20 ml) and dried under vacuumat 80° C. to give the 3,4,5-tribromopyrazole (1) in the form of anoff-white solid (30 g, 67%).

[0063]¹³C NMR (100 MHz, d₆-DMSO): 97.7, 116.1, 126.4

[0064] melting point: 182-184° C.

[0065] Synthesis of 3,5-dibromo-4-nitropyrazole (2):

[0066] HNO₃ (d=1.50 g/ml; 18 ml, 0.429 mol) was added dropwise over 10minutes to a solution of 3,4,5-tribromopyrazole (1) (50 g, 0.164 mol) inglacial acetic acid (750 ml) while maintaining the temperature at 15° C.Acetic anhydride (250 ml) was added and the reaction mixture was stirredat room temperature for 2 hours. Once the reaction was complete, thereaction mixture was poured onto crushed ice (1 kg). After stirring for1 hour, the crude product was filtered off and then washed withdemineralized water (2×60 ml) to give crude1-nitro-3,4,5-tribromopyrazole. The water (24.6 ml) contained in the wetproduct was removed by heating a solution of the product in toluene (750ml) at reflux in Dean-Stark apparatus. The toluene solution wasmaintained at reflux for a further 30 minutes until a TLC (eluent:toluene) showed that the rearrangement of the1-nitro-3,4,5-tribromopyrazole (Rf=0.77), the intermediate formed, into3,5-dibromo-4-nitropyrazole 2 (Rf=0.05) was complete. The solution wasconcentrated to a residual volume of 150 ml and then allowed to cool to60° C., followed by addition of hexane (275 ml). The solution was cooledto 0-5° C. for 1 hour and the 3,5-dibromo-4-nitropyrazole (2) (29.1 g,65%) was recovered by filtration and drying under vacuum in the form ofa pale yellow solid.

[0067] melting point: 127.6-130.1° C.

[0068] Synthesis of 3-(3,5-dibromo-4-nitropyrazol-1-yl)propan-1-ol(3-1):

[0069] A mixture of 3,5-dibromo-4-nitropyrazole (2) (2.0 g; 7.38 mmol)in DMF (9.5 ml) was added over 15 minutes to a suspension of NaH (0.32g, 8.0 mmol; 60% dispersion in oil, prewashed with hexane) in DMF (16ml) with stirring and under an inert atmosphere. After stirring for 15minutes, a solution of 3-bromo-1-propanol (1.0 g; 7.19 mmol) in DMF (3.2ml) was added dropwise. The reaction mixture was heated at 80° C. for 2hours (monitored by TLC) and the DMF was then evaporated off underreduced pressure. A mixture of DCM/water (20 ml, 1/1) was added. Theorganic phase was dried over Na₂SO₄ and the solvent was evaporated offunder reduced pressure. The crude reaction product was obtained as ablack oil (1.9 g, 79%), which was used without further purification inthe amination step.

[0070] Synthesis of 1-propyl-3,5-dibromo-4-nitropyrazole (3-2):

[0071] A mixture of 3,5-dibromo-4-nitropyrazole (2) (25 g, 92 mmol) inDMF (120 ml) was added over 45 minutes to a suspension of NaH (4.0 g, 10mmol; 60% dispersion in oil, prewashed with hexane) in DMF (200 ml) withstirring and under an inert atmosphere. After stirring for 30 minutes, asolution of 1-bromopropane (13.6 g, 111 mmol) in DMF (40 ml) was addedover 10 minutes. The reaction mixture was heated at 50-60° C. for 3hours (monitored by TLC) and the DMF was then evaporated off underreduced pressure. A mixture of DCM/water (300 ml, 1/5) was added and theorganic phase was then extracted with water (2×50 ml). The organic phasewas dried over Na₂SO₄ and the solvent was evaporated off under reducedpressure. The crude reaction product was obtained as a black oil (19.4g, 70%), which was used without further purification in the aminationstep.

[0072] Synthesis of 1- (3,5-dibromo-4-nitropyrazol-1-yl) propan-2-ol(3-3):

[0073] A mixture of 3,5-dibromo-4-nitropyrazole (2) (40.0 g; 147 mmol)in DMF (200 ml) was added over 15 minutes to a suspension of NaH (6.5 g,162 mmol; 60% dispersion in oil, prewashed with hexane) in DMF (320 ml)with stirring and under an inert atmosphere. After stirring for 35minutes, a solution of 1-bromo-2-propanol (26.8 ml; 221 mmol) in DMF (80ml) was added dropwise. The reaction mixture was heated at 80° C. for 2hours and the DMF was then evaporated off under reduced pressure. Amixture of DCM/water (480 ml, 2/1) was added. The organic phase wasextracted with DCM (2×160 ml). The combined organic phases were washedwith water (3×400 ml) . The organic phase was dried over Na₂SO₄ and thesolvent was evaporated off under reduced pressure. The 1-(3,5-dibromo-4-nitropyrazol-1-yl)-propan-2-ol was obtained as a whitesolid (23.3 g; 48%) .

[0074] R_(f) (DCM/MeOH: 95/5)=0.8

[0075] 00 MHz, d⁶-DMSO) : 5.10 (1 H, d, OH), 4.22-4.02 (3 H, m_(broad),CH₂CH and CH₂CH) , 1.15 (3 H, d, CH₃) .

[0076] Synthesis of 3-(3,5-dibromo-4-nitropyrazol-1-yl)-propane-1,2-diol (3-4):

[0077] A mixture of 3,5-dibromo-4-nitropyrazole (2) (40.0 g; 147 mmol)in DMF (200 ml) was added over 15 minutes to a suspension of NaH (6.5 g,162 mmol; 60% dispersion in oil, prewashed with hexane) in DMF (320 ml)with stirring and under an inert atmosphere. After stirring for 30minutes, a solution of 3-bromo-1,2-propanediol (19.4 ml; 221 mmol) inDMF (80 ml) was added dropwise. The reaction mixture was heated at 80°C. for 3 hours and the DMF was then evaporated off under reducedpressure. A mixture of DCM/water (480 ml, 2/1) was added. A yellow solidprecipitated out. After washing with ether (50 ml), the3-(3,5-dibromo-4-nitropyrazol-1-yl)-propane-1,2-diol (32.3 g, 63%) wasobtained as a white solid (23.3 g; 48%).

[0078] R_(f) (DCM/MeOH: 90/10)=0.35 ¹H NMR (200 MHz, d⁶-DMSO): 5.09 (1H, d, CHOH), 4.80-4.75 (1 H, t_(broad), CH₂OH), 4.27-4.15 (2 H, m,CH₂OH), 3.35-3.29 (3 H, m, N—CH₂CH and CH₂CH).

[0079] Synthesis of3-(5-benzylamino-3-bromo-4-nitropyrazol-1-yl)propan-1-ol (4-1):

[0080] A mixture of 3-(3,5-dibromo-4-nitropyrazol-1-yl)propan-1-ol (3-2)(17.1 g, 52 mmol), EtOH (100 ml) and benzyl-amine (27.9 g, 260 mmol) wasrefluxed for 15 hours. The reaction medium was concentrated to themaximum under reduced pressure. The highly viscous residue was suspendedin EtOAc (100 ml) and EtOH (100 ml). The organic phase was washed withNaCl solution (10%, 100 ml) and then dried over Na₂SO₄. Afterevaporating off the solvent under reduced pressure, an orange-coloredoil was obtained (13.6 g), which was subsequently purified by columnchromatography (gradient: 10%/90% EtOAc/hexane to 40%/60% EtOAc/hexane)in order to obtain, after evaporating off the solvent, the3-(5-benzylamino-3-bromo-4-nitropyrazol-1-yl)propan-1-ol in the form ofa yellow solid (8.8 g, 48 %) .

[0081] melting point: 95.0-96.5° C.

[0082]¹H NMR (400 MHz, CDCl₃): 7.40-7.30 (5 H, m, H_(Ar)) ; 4.68

[0083] (2 H, d, J=7. 0 Hz, NHCH₂), 4.16 (2 H, t, J=7.0 Hz, CH₂N), 3.65(2 H, t, J=7.0 Hz, CH₂O); 2.02 (2 H, m, CH₂CH₂CH₂).

[0084] Synthesis ofbenzyl(5-bromo-4-nitro-2-propyl-1H-pyrazol-3-yl)amine (4-2):

[0085] A mixture of 1-propyl-3,5-dibromo-4-nitropyrazole (19.4 g, 62mmol), EtOH (500 ml) and benzylamine (40 g, 373 mmol) was refluxed for15 hours. The reaction medium was concentrated to the maximum underreduced pressure. The residue was suspended in EtOAc (100 ml ), theinsoluble part was separated out by filtration and the filtrate wasevaporated to dryness. The black oil obtained was purified by columnchromatography (eluent: EtOAc/hexane) to give thebenzyl(5-bromo-4-nitro-2-propyl-2H-pyrazol-3-yl)amine in the form of ayellow solid (9 g; 29%) from 3,5-dibromo-4-nitropyrazole.

[0086] melting point: 91.8-92.3° C. ¹H NMR (400 MHz, CDCl₃): 7.41-7.31(5 H, m, H_(arom)) ; 4. 61 (2 H, d, J=6.5 Hz, NHCH₂), 3.94 (2 H, t,J=7.5 Hz, CH₂N), 1.83 (2 H, m, CH₃CH₂), 0.89 (3 H, t, J=7.5 Hz, CH₃).

[0087] Synthesis of1-(5-benzylamino-3-bromo-4-nitropyrazol-1-yl)propan-2-ol (4-3):

[0088] A mixture of 1-(3,5-dibromo-4-nitropyrazol-1-yl)propan-2-ol (3-3)(22 g, 666 mmol), EtOH (300 ml) and benzylamine (102 g, 936 mmol) wasrefluxed for 1.5 hours. The reaction medium was concentrated to themaximum under reduced pressure. DCM (100 ml) was added to the residue.The organic phase was washed with dilute acid (5×50 ml). The organicphase was dried over Na₂SO₄ and the solvent was evaporated off underreduced pressure. The brown oil obtained was treated with diisopropylether at 0° C. to give the1-(5-benzyl-amino-3-bromo-4-nitropyrazol-1-yl)propan-2-ol (13.7 g, 58%)in the form of a yellow solid.

[0089] melting point: 81.3° C.

[0090] m/z (ES⁺): 355 [M+H]⁺; 377 [M+Na]⁺; 733 [2M+Na]⁺.

[0091] Synthesis of3-(5-benzylamino-3-bromo-4-nitropyrazol-1-yl)propane-1,2-diol (4-4):

[0092] A mixture of 1-(3,5-dibromo-4-nitropyrazol-1-yl)-propane-1,2-diol(3-4) (31 g, 898 mmol), EtOH (420 ml) and benzylamine (138 g, 1.26 mol)was refluxed for 1.5 hours. The reaction medium was concentrated to themaximum under reduced pressure. 100 ml of DCM were added to the residue.The organic phase was washed with dilute acid (5×50 ml). The organicphase was dried over Na₂SO₄ and the solvent was evaporated off underreduced pressure. The brown oil obtained was treated with diisopropylether at 0° C. to give the3-(5-benzyl-amino-3-bromo-4-nitropyrazol-1-yl)propane-1,2-diol (14.1 g,42%) in the form of a yellow solid.

[0093] melting point: 90.1° C.

[0094] m/z (ES⁺): 372 [M+H]⁺; 395 [M+Na]⁺; 767 [2M+Na]⁺.

[0095] Synthesis of 3-(4,5-diaminopyrazol-1-yl)propan-1-ol hydrobromideand hydrochloride (5-1):

[0096] A mixture of3-(5-benzylamino-3-bromo-4-nitropyrazol-1-yl)propan-l-ol (4-1) (8.8 g;24.8 mmol) in EtOH (500 ml) containing 10% Pd/C as catalyst(Johnson-Mattey Type 487, 0.9 g dry weight) and 36% hydrochloric acid(6.0 g, 59 mmol) was hydrogenated in an autoclave (1 1) at 11 bar for 5hours. The catalyst was filtered off and washed with EtOH, and thefiltrate was evaporated under reduced pressure. Under an inertatmosphere, the crude oil was taken up in EtOH (50 ml) and heated to 50°C. EtOAc (50 ml) was added and the mixture was cooled first to roomtemperature and then to 0-5° C. over 2 hours. The precipitate formed wasrecovered by filtration, washed with a cold mixture of EtOH/EtOAc (1/1,2×30 ml) and dried under vacuum to give the3-(4,5-diaminopyrazol-1-yl)propan-1-ol in the form of the hydrobromideand hydrochloride (1.06 eq HBr and 0.94 eq HCl) as an off-white solid(2.4 g, 42%).

[0097] melting point: 275-280° C. elemental analysis: C₈H₁₄N₄O (1.06HBr, 0.94 HCl) found: C: 26.13%, H: 5.13%, N: 20.09%, O: 5.92%, Br:29.05%, Cl: 12.60% theory: C: 26.34%, H: 5.16%, N: 20.48%, 0: 5.85%, Br:29.21%, Cl: 12.96% ¹H NMR (400 MHz, d⁶-DMSO): 8.26 (1 H, s, H_(py));5.18 (1 H, S_(broad), NH), 4.02 (2 H, m, CH₂N), 3.45 (2 H, m, CH₂O),1.85 (2 H, m, CH₂)

[0098] Synthesis of 4, 5-diamino-1-propylpyrazole hydrobromide andhydrochloride (5-2):

[0099] A mixture of benzyl(5-bromo-4-nitro-2-propyl-2H-pyrazol-3-yl)amine (7 g; 21 mmol) in EtOH(500 ml) containing 10% Pd/C as catalyst (Johnson-Mattey Type 487, 0.5 gdry weight) and 36% hydrochloric acid (5.0 g, 49 mmol) was hydrogenatedin a Parr autoclave (1 1) at 11 bar for 3 hours. The catalyst wasfiltered off and washed with EtOH, and the filtrate was evaporated underreduced pressure. Under an inert atmosphere, the crude orange oil wastaken up in EtOH and heated to 40° C. EtOAc (90 ml) was added and themixture was maintained at room temperature for 15 hours. The precipitateformed was recovered by filtration, washed with a cold mixture ofEtOH/EtOAc (1/1, 2×20 ml) and dried under vacuum to give the4,5-diamino-1-propylpyrazole in the form of the hydrobromidehydrochloride (0.55 eq HBr and 1.38 eq HCl) as an off-white solid (2.5g, 57%).

[0100] melting point: 168.1-173.0° C. elemental analysis: C₆H₁₂N₄ (0.55HBr, 1.38 HCl) found: C: 29.08%, H: 6.06%, N: 22.87% theory: C: 27.98%,H: 5.48%, N: 21.75% ¹H NMR (400 MHz, d⁶-DMSO): 7.34 (1 H, s, H_(py));5.18 (1 H, S_(broad), NH); 4.09 (2 H, t, J=5.5 Hz, CH₂N); 3.61 (2 H, t,J=5.5 Hz, CH₂O); 3.23 (3 H, s, OCH₃) .

[0101] Synthesis of 1-(4,5-diaminopyrazol-1-yl)propan-2-ol hydrobromide(5-3):

[0102] A mixture of 1-(5-benzylamino-3-bromo-4-nitropyrazol-1-yl)propan-2-ol (4-3) (5.0 g;14.0 mmol) in EtOH (140 ml) containing 10% Pd/C as catalyst (Engelhard,50% wet, 0.5 g dry weight) and NaOH (solid, 560 mg, 14 mmol) washydrogenated in an autoclave (1 l) at 11 bar for 2 hours. The reactionmixture was filtered to remove the catalyst, under an inert atmospherein an ethanolic solution containing HBr (47%, 9.7 ml, 78 mmol). Thesolvent was evaporated off under reduced pressure to give a solid. Afterwashing with cold EtOH, the 1-(4,5-diaminopyrazol-1-yl)propan-2-ol wasobtained in the form of the hydrobromide (3.47 eq HBr) as a white solid(2.3 g, 42%).

[0103] melting point: 222.3° C. elemental analysis: C₆H₁₂N₄O (3.47 HBr)found: C: 15.75%, H: 3.03%, N: 11.54%, O: 4.15%, Br: 59.26% theory: C:15.02%, H: 3.36%, N: 11.68%, O: 3.33%, Br: 66.61% ¹H NMR (400 MHz,d⁶-DMSO): 7.72 (1 H, s, CH_(arom)); 7.66-6.20 (7 h, S_(broad), NH₂ andOH and HBr); 4.23-4.07 (3 H, m, NCH₂CH and NCH₂CH); 1.29 (3 H, d, CH₃).

[0104] Synthesis of 3-(4,5-diaminopyrazol-1-yl)propane-1,2-diolhydrobromide (5-4):

[0105] A mixture of3-(5-benzylamino-3-bromo-4-nitropyrazol-1-yl)propane-1,2-diol (4-4) (7.0g; 18.8 mmol) in EtOH (150 ml) containing 10% Pd/C as catalyst(Engelhard, 50% wet, 0.7 g dry weight) and NaOH (solid, 800 mg, 18.8mmol) was hydrogenated in an autoclave (1 l) at 16 bar for 3.5 hours.The reaction mixture was filtered to remove the catalyst under an inertatmosphere, in an ethanolic solution containing HBr (47%, 7.1 ml, 57mmol). The solvent was evaporated off under reduced pressure to give asolid. After washing with cold EtOH, the3-(4,5-diaminopyrazol-1-yl)propane-1,2-diol hydro-bromide was obtainedas an off-white solid.

[0106]¹H NMR (400 MHz, d⁶-DMSO): 7.90 (1 H, s, H_(arom)); 4.30-4.14 (3H, m, NCH₂CH and NCH₂CH); 3.69-3.60 (2 H, m, CH₂OH).

Formulation Examples in Alkaline Medium

[0107] The dye formulations below are prepared: 4, 5-diaminopyrazole offormula (I) 5 × 10⁻³ mol coupler 5 × 10⁻³ mol oleyl alcoholpolyglycerolated with 4.0 g 2 mol of glycerol oleyl alcoholpolyglycerolated with 5.7 g A.M. 4 mol of glycerol, containing 78%active material (A.M.) oleic acid 3.0 g oleylamine containing 2 mol ofethylene 7.0 g oxide, sold under the trade name Ethomeen 012 by thecompany Akzo diethylaminopropyl laurylamino succinamate, 3.0 g A.M.sodium salt, at 55% A.M. oleyl alcohol 5.0 g oleic acid diethanolamide12.0 g propylene glycol 3.5 g ethyl alcohol 7.0 g dipropylene glycol 0.5g propylene glycol monomethyl ether 9.0 g sodium metabisulfite as anaqueous 0.455 g A.M. solution containing 35% A.M. ammonium acetate 0.8 gantioxidant, sequestering agent qs fragrance, preserving agent qsaqueous ammonia containing 20% NH₃ 10 g

[0108] The pH of the composition is 9.5

[0109] A.M. means “active material” Examples Base Coupler 1 3-(4-,5diaminopyrazol-1- 5-amino-6-chloro-2- yl)propan-1-ol, 1.06 HBr,methylphenol 0.94 HCl (5-1) 2 3-(4-,5 diaminopyrazol-1- 1β-hydroxyethoxy- yl)propan-1-ol 1.06 HBr, 2,4-diaminobenzene, 0.94 HCl(5-1) 2 HCl 3 2-propyl-2H-pyrazole-3,4- 5-amino-6-chloro-2- diamine 0.55HBr, 1.38 HCl methylphenol (5-2) 4 2-propyl-2H-pyrazole-3,4- 1β-hydroxyethoxy- diamine 0.55 HBr, 1.38 HCl 2,4-diaminobenzene, (5-2) 2HCl

[0110] At the time of use, each dye composition is mixed, weight forweight, with a 20-volumes aqueous hydrogen peroxide solution (6% byweight), the pH of which has been adjusted to about 2.5 withorthophosphoric acid.

[0111] The mixture is applied to natural or permanent-waved grey haircontaining 90% white hairs, at a rate of 5 g per 0.5 g of hair, for 30minutes.

[0112] The hair is then rinsed, washed with a standard shampoo anddried.

[0113] The color of the locks was evaluated in the L*a*b* system, onwhite and permanent-waved hair, using a Minolta CM 2002spectrophotometer.

[0114] In the L*a*b* space, the lightness is indicated by the value L*on a scale from 0 to 100, while the chromatic data is expressed by a*and b* which indicate two color axes, a* the red-green axis and b* theyellow-blue axis.

[0115] According to this system, the higher the value of L, the palerand less intense the color. Conversely, the lower the value of L, thedarker or more intense the color. Natural white hair Permanent-wavedwhite hair Examples L* a* b* L* a* b* Example 1 35.9 33.3 16.9 33.1 33.416.4 Example 2 22.5 22.7 1.0 18.2 17.1 1.9 Example 3 33.9 32.9 15.1 30.831.2 14.9 Example 4 20.9 21.2 −0.2 17.6 14.6 1.24

[0116] The 4,5-diaminopyrazoles according to the invention thus make itpossible to obtain strong and chromatic shades at alkaline pH.

Formulation Examples in Neutral Medium

[0117] The same formulations as above are prepared, replacing theaqueous ammonia with citric acid in an amount such that the pH of thecomposition is equal to 7 and starting with the bases and couplersbelow. Examples Base Coupler 5 3-(4-,5 diaminopyrazol-1-yl)- 2-methyl-5-propan-1-ol, HBr, HCl (5-1) aminophenol 6 2-propyl-2H-pyrazol-3,4-2-methyl-5- diamine, HBr, HCl (5-2) aminophenol

[0118] Locks of natural and permanent-waved gray hair containing 90%white hairs are dyed with the dye compositions 5 and 6 above in the samemanner as for the dyeing at alkaline pH.

[0119] The following shades are obtained: Natural white hairPermanent-waved white hair Examples L* a* b* L* a* b* Example 5 39.531.6 26.7 32.8 33.8 25.7 Example 6 37.3 25.6 19.7 29.9 28.7 19.7

[0120] At neutral pH, the 4,5-diaminopyrazoles according to theinvention make it possible to obtain strong chromatic shades.

1. A diaminopyrazole compound of formula:

in which R₁ denotes a linear or branched C₄-C₅ n-propyl or alkyl group,or a linear or branched C₃-C₅ mono- or polyhydroxyalkyl group, and thephysiologically acceptable acid salts thereof:
 2. The compound offormula (I) as claimed in claim 1, characterized in that thephysiologically acceptable salts are acid salts chosen from thehydrochlorides, hydrobromides, sulfates, tartrates, lactates andacetates.
 3. The compound of formula (I) as claimed in claim 1 or 2,characterized in that R₁ a linear or branched n-propyl; butyl or pentylgroup; linear or branched propyl, butyl or pentyl group, which issubstituted by 1 to 4 OH radicals.
 4. The compound of formula (I) asclaimed in any one of claims 1 to 3, characterized in that it is2-propyl-2H-pyrazole-3,4-diamine and3-(4,5-diaminopyrazol-1-yl)propan-1-ol, or a physiologically acceptableacid salt thereof.
 5. A composition for the oxidation dyeing of keratinfibers, and in particular of human keratin fibers such as the hair,characterized in that it contains, in a medium that is suitable fordyeing, as oxidation base, at least one 4,5-diaminopyrazole of formula(I):

in which R₁ denotes a linear or branched C₄-C₅ n-propyl or alkyl groupor a linear or branched C₃-C₅ mono- or polyhydroxyalkyl group, or anaddition physiologically acceptable acid salt thereof.
 6. Thecomposition as claimed in claim 5, characterized in that it containsfrom 0.001% to 10% by weight of at least one diaminopyrazole of formula(I) or salt thereof.
 7. The composition as claimed in claim 6,characterized in that it contains from 0.05% to 6% by weight andpreferably 0.1% to 3% by weight of at least one diaminopyrazole offormula (I) or salts thereof.
 8. The composition as claimed in any oneof claims 5 to 7, characterized in that the medium that is suitable fordyeing consists of water or of a mixture of water and at least oneorganic solvent chosen from C₁-C₄ lower alkanols, polyols and polyolethers, aromatic alcohols, similar products and mixtures thereof.
 9. Thecomposition as claimed in any one of claims 5 to 8, characterized inthat it has a pH of between 3 and
 12. 10. The composition as claimed inany one of claims 5 to 9, characterized in that it contains at least oneadditional oxidation base chosen from para-phenylenediamines,bis(phenyl)alkylenediamines, para-aminophenols, ortho-aminophenols andheterocyclic bases other than the N-substituted diaminopyrazole offormula (I), and addition acid salts thereof.
 11. The composition asclaimed in claim 10, characterized in that the additional oxidationbase(s) represent(s) from 0.0005% to 12% by weight relative to the totalweight of the dye composition.
 12. The composition as claimed in any oneof claims 5 to 11, characterized in that it contains at least onecoupler and/or at least one direct dye.
 13. The composition as claimedin claim 12, characterized in that the coupler(s) is (are) chosen frommeta-phenylenediamines, meta-aminophenols, meta-diphenols, mono- orpolyhydroxylated naphthalene derivatives and heterocyclic couplers, andthe addition acid salts thereof.
 14. The composition as claimed ineither of claims 12 and 13, characterized in that the coupler(s)represent(s) from 0.0001% to 10% by weight relative to the total weightof the dye composition.
 15. The composition as claimed in any one ofclaims 5 to 14, characterized in that the addition acid salts are chosenfrom the hydrochlorides, hydrobromides, sulfates, tartrates, lactatesand acetates.
 16. A process for dyeing keratin fibers, and in particularhuman keratin fibers such as the hair, characterized in that at leastone dye composition as defined in any one of claims 5 to 15 is appliedto these fibers, for a time that is sufficient to develop the desiredcoloration, either in air or using an oxidizing agent, optionally in thepresence of oxidation catalysts.
 17. The process as claimed in claim 16,characterized in that the coloration is revealed solely on contact withatmospheric oxygen.
 18. The process as claimed in claim 16,characterized in that the color is revealed at acidic, neutral oralkaline pH with the aid of an oxidizing agent, which is added to thedye composition just at the time of use, or which is present in anoxidizing composition applied simultaneously or sequentially in aseparate manner.
 19. The process as claimed in claim 16 or 18,characterized in that the oxidizing agent is chosen from hydrogenperoxide, urea peroxide, alkali metal bromates and persalts such asperborates and persulfates.
 20. A multi-compartment device ormulti-compartment dyeing “kit”, a first compartment of which contains adye composition as defined in any one of claims 5 to 15, and a secondcompartment of which contains an oxidizing composition.